Category: New Research Page 53 of 67

It’s immediately clear to anyone visiting the Greater Antilles that humans have had a dramatic impact on natural environments.  Even in those areas that remain forested and seemingly pristine, it isn’t difficult to find the stray coffee bush or mango tree.  Indeed, some understory crops, such as coffee and cacao, have traditionally been grown under an intact canopy.  These traditional practices have been changing over the past few decades, however, as large commercial operations have favored the efficiency of clear-cutting and subsequent cultivation in open sun.  The impacts of this shift from shade to sun cultivation on biodiversity have been debated for decades, with most studies indicating overall losses in biodiversity and super-abundance of a few common species in sun plantations.

In spite of the prevalence of agriculture in the Greater Antilles, relatively few studies have investigated the abundance of anoles and other lizards in different types of agriculturally disturbed habits (but see my first first authored paper!).  A new study by Borkhataria et al. (2012) conducts a comparative analysis of species abundance of birds, anoles, and invertebrates in shade versus sun coffee on Puerto Rico.  This study is a welcome addition to the literature because the portion of coffee on Puerto Rico grown in sun plantations has doubled in recent years, although overall coffee production has declined.

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Few anole species have been responsible for as much taxonomic confusion as the widespread Amazonian species Anolis chrysolepis.  It wasn’t even until 2008 that taxonomists decided once and for all that this species should be called A. chrysolepis (Duméril & Bibron 1837), rather than A. nitens (Wagler 1830) (Mayer 2008 successfully petitioned for recognition of  A. chrysolepis on the grounds that Wagler’s Draconura nitens was a nomen dubium due to the absence of a holotype and an exceptionally vague 4-line description and locality [“America”]).

Largely because of its broad range and remarkable geographic variation in size, shape, and coloration, Anolis chrysolepis has attracted the attention of herpetologists for generations.  

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Elise Knowlton, a graduate student in Manuel Leal’s Lab at Duke University, reports on the initiation of her field research on mating behavior in green anoles in North Carolina

The pug-nosed anole, as it is known, is a pretty weird species. First is its funny-looking face, hence it’s name. Second, it is very unusual among anoles in being relatively large, yet found almost invariably near the ground–most larger anoles are found higher up in the tree. Finally, it’s long legs are ungainly and seemingly awkward. Relatively little is known about its natural history, and there is some indication that in some places, it may have become less common.

Our knowledge of natural history knowledge was expanded ever so slightly by the recent report by Mora et al. in the most recent Herpetological Review of an observation of a male eating a pygmy rain frog (Pristimantis ridens). 

Think Caribbean lizard diversity and you think of anoles, dwarf geckos, perhaps curly tailed lizards and whiptails. But skinks don’t generally come to mind. Heck, I almost never see skinks in the Caribbean and, anyway, their diversity is very low, with only six Caribbean species.

Until now. In a recently published monograph, Hedges and Conn have scrutinized the genus Mabuya, using both molecular and morphological characters, and have more than doubled the number of species, from 26 to 61, which they have broken into 16 genera (and, as a sidenote, they also split the family Scincidae into seven families). That so many species went undetected is perhaps not surprising, in that Mabuya, like most skinks, all look alike, with very few characters available to distinguish them. Moreover, a trend of species lumping has occurred historically, obscuring sometimes great differences among taxa, as illustrated in the photo to the left.

Of the 61 species, 39—in six genera—occur on Caribbean islands. Most occur on a single island, and most islands only have one species, though as many as three occur on Hispaniola and St. Thomas, and two on a number of islands. Oddly, Cuba has none. Like anoles, to which they no doubt aspire,

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Lizards have become a staple of laboratory studies of locomotion. A standard approach, honed to perfection over 30 years of such work, is to get a lizard to run down a narrow trackway or on a dowel to determine how fast it can run and, in recent years via high speed video, to see exactly how the different limb elements move. Questions that one might ask include whether long-legged lizards run faster than their short-legged compatriots, whether species can run faster on broad surfaces as compared to on narrower supports, or whether the loss of a tail affects sprint speed. In fact, the sort of questions one might ask about lizard locomotion are virtually endless.

These studies have one Achilles heel, however, Most such studies focus on examining maximum speed of the lizard, but how can one ensure that lizards are actually running full tilt? The nagging fear has always been that differences in speed might result not for different capabilities, but rather as a result of differential motivation–some lizards just want it more than others.

But how can one elicit maximal speed or investigate whether a lizard is holding back? One approach to this question was revealed in a recent paper in J. Herp. Jones and Jayne tested whether a loud noise might cause a lizard to run faster and the answer is: yes, when subjected to repeated loud noises, lizards in experimental race tracks do, in fact, run faster.

And just what kind of loud noise? Let’s let junior author Bruce Jayne explain the genesis of the study:

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Although devoted to all things Anolis, Anole Annals strives to keep its readers updated on relevant findings concerning other lizards. In that vein, we’ve just learned of a newly completed thesis on lacertid lizards on European islands by Anna Runemark at Lunds University, under the supervision of Erik Svensson. Here’s the English summary of her thesis, from this page, and some remarks from Erik here. Her defense is on May 25th. Good luck, Anna!

“Islands are cradles for new biodiversity and provide natural laboratories for the study of population divergence. In my thesis, I investigated the role of different evolutionary processes in the population divergence in the Skyros wall lizard (Podarcis gaigeae), a species where islet populations have strongly diverged morphologies. I used replicate islet populations and their respective most proximate mainland populations to investigate how divergence has proceeded following the isolation of the islets. First, I combined bathymetric maps with sea level curves and molecular inferences based on Bayesian statistics to investigate the biogeographical history of populations. I found that islet populations have become isolated by vicariance following sea level rises during the last thousands of years, and no significant gene flow between populations. To investigate which processes are affecting population divergence, I studied patterns of divergence in coding genetic variation, traits assumed to be under simple Mendelian inheritance, morphological and behavioral traits. A clear pattern of parallel adaptive divergence in the islet environment emerged for traits mainly subjected to natural selection. Islet lizards were larger, greener and less prone to escape. Islet lizards were also less cryptic in their environments than were mainland lizards. Moreover, between-population variation in size and color was larger for islet- than for mainland populations. These patterns are indicative of a predation release. I also found that islet lizards have relatively wider and differently shaped heads as well as a stronger bite force in relation to mainland populations. Data on available food and realized diet suggest that these changes are adaptations to harder island diet. Together these data suggest that predation release and selection for a diet change have interacted and jointly driven the evolution of larger body sizes on islands.

No general pattern of parallel divergence was found for traits subjected primarily to sexual selection. Instead, divergence in throat color morph frequency and sex pheromone composition were significantly correlated with neutral genetic divergence. This indicates that stochastic processes such as genetic drift have contributed to divergence of these traits. I also investigated if mate preferences for pheromones, throat color and body size could be driving population divergence. I found no population differences in preferences for throat color and body size, suggesting that mate choice does not drive divergence in these characters. Islet populations did, however, prefer scent from islet lizards, whereas mainland lizards were less discriminatory. This implies that there could be some mate discrimination against mainland lizards that disperse to islets. 

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For those of us that study embryonic and juvenile development this is an exciting time. The first anole eggs of the season are here!

The prize for first egg of the season goes to Anolis distichus. Fifteen females were collected in Miami one week ago ago and I collected 11 eggs from their cages yesterday. A. carolinensis, A. sagrei, and A. cristatellus seem to be off to a slower start. Of the 12 A. sagrei females collected I only found two eggs while the other species have yet to produce any.  My fingers are crossed that egg production picks up soon.

Is anyone else out there having any early season luck? Which species? Are people in the field observing regular mating behaviors now?

In a gargantuan recent paper in Comparative Parasitology, Bursey, Goldberg, Telford and Vitt report new data for 13 Central American anoles and summarize what is known about helminths through all of anoledom. Before getting into the details, though, it may help some of our readers to explain what a helminth is. In short, helminths are parasitic worms, such as nematodes, flukes, and tapeworms; anoles—and many other animals—are commonly infested with them.

Prior to this study, helminths had only been reported in 10 Central American anoles. However, taking advantage of the collections of Telford and Vitt, dating back to late 1950’s, the researchers examined 426 anoles of 13 species, basically opening up museum specimens to see what surprises awaited. The result was 1026 parasites found in 173 of the specimens.

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